How silky and shiny your spandex remains really comes down to how much punishment you subject it to while wearing it. If you're rock climbing or running an obstacle course wearing your favorite Amoresy full suit, don't expect that lovely shine to last indefinitely. Abrasion from rough surfaces will naturally destroy the finish of even the most expensive spandex. I've personally found that this tends to occur more with a polyester/spandex blend. I've got some tights I bought back in the 80's that are a nylon/spandex blend and they still look great.
Wash your gear using cold water and a gentle soap, and NEVER put spandex in a dryer. Lay it flat out of direct sunlight, or throw it over the shower curtain rod to dry. I realize some guys are into crusty stains and such, but certain bodily fluids are acidic and should be washed out as soon as possible. Take good care of your spandex and there's no reason you can't expect to enjoy it for years.